This invention relates to an automotive vehicle, and especially to a vehicle that includes a plastic outer body and an interior metal support frame for the plastic outer body. In preferred practice of the invention the plastic outer body is a one-piece plastic molding formed in a one-step operation by a blow-molding process or a centrifugal casting process.
Such molding processes advantageously enable the plastic outer body to have hollow wall areas at selected points, whereby the body is reinforced against bending, twisting or deformation. The blow-molding process is advantageous in that it has a relatively fast cycle time. The centrifugal casting process is advantageous in that it produces smooth surfaces free of mold marks; also the centrifugal casting process enables the color of the plastic body to be changed after each mold cycle, which is advantageous in short production runs.
A general advantage of a plastic outer body is that it is resistant to attack by gasoline, oil, grease and other chemicals. Plastic is easy to clean, and is resistant to corrosion and ultra violet rays. The plastic material herein envisioned will not crack, chip or break at elevated temperatures normally encountered in normal vehicle use.
The invention contemplates a modified monocoque vehicle design, wherein major loads are transferred between a plastic body and a metal support frame (or chassis). In this regard, the term "monocoque" refers to a vehicle body that relies on a light weight shell to bear the principal stresses. In the present invention a strong hollow-walled plastic shell is combined with a rigid metal frame so that the shell and frame share the major stresses.
The composite vehicle body structure of the present invention is designed so that the frame component can be used as a cooling fixture for supporting the plastic outerbody while the plastic component is cooling (i.e. immediately after the plastic outerbody has been formed). This feature greatly simplifies the material handling process in the manufacturing facility.
In preferred practice of the invention the plastic body component is a single plastic member formed by a blow molding operation or a rotational casting process. However, the plastic body component can alternately formed by two or three interchangeable body sections securable together by mechanical or adhesive connections in "leggo" fashion. By employing plural interchangeable body sections it is possible to change the manufacturing from four seat to a five seat vehicle very quickly (e.g. in hours). This feature provides great marketing flexibility.
The metal frame component of the composite vehicle is preferably located entirely within the plastic outerbody. However, in extended practice of the invention the metal frame component could be at least partially outside the plastic component. For example, portions of the metal at the front and rear ends of the vehicle could be located outside the plastic shell to form front and rear bumpers.
Important advantages achieved by the invention are cost reduction and weight reduction. Hollow-wall sections resulting from the molding process greatly stiffen and rigidify the plastic outerbody so as to greatly reduce the need for extraneous reinforcement mechanisms that add to overall vehicle weight.
Preferably the vehicle body is designed so that the plastic body component has no metal inserts permanently attached to the plastic material. Should it be necessary to convert the vehicle to scrap (after it's useful life) the metal frame can be separated from the plastic outerbody; the lack of metal inserts in the plastic body enables the plastic material to be readily recycled without excessive labor costs.
In preferred practice of the invention the plastic body component is formed out of a thermoplastic material (rather than a thermoset plastic). The molded plastic is a pure homogenous material that can be repaired, if necessary, by the use of fusion equipment. In this sense, the plastic body material differs from reinforced fiber-plastic composites heretofore used in some plastic vehicle structures and plastic boat structures.
The plastic outer body is preferably formed by a blow-molding operation, using a thermoplastic polyolefin material in an extruded parison form. However, the plastic outer body can also be formed by a rotational casting process. Further features of the invention will be apparent from the attached drawing and description of an illustrative embodiment of the invention.